1. Field of the Invention
The present invention relates generally to communication equipment and, more specifically but not exclusively, to header-compression modules of network nodes in packet-based communication systems.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Header compression is a process of compressing a packet header before transmitting the corresponding packet over a communication link and then decompressing the header to its original state upon reception at the remote end of the link. Header compression is typically possible because header fields of different packets of the same packet stream have redundant information. For example, by observing the fields that remain constant or change in specific patterns, the transmitter can either omit these fields in some packets or represent these fields in fewer bits compared to the original size.
In data-streaming applications that operate in accordance with Internet Protocol (IP) version 4 or version 6, the combined IP/UDP (User Datagram Protocol)/RTP (Real-time Transport Protocol) header size is 40 or 60 bytes, respectively. For Voice over IP (VoIP), these sizes may correspond to about 60% of the total amount of data sent over the communication link. While the overhead of this size may be tolerable on wired links, it is usually deemed excessive for wireless links where the bandwidth is a scarce resource. Therefore, an efficient compressor that is able to reduce the header size from 40 or 60 bytes down to several (e.g., one to three) bytes is an extremely useful component to have on communication links with a limited bandwidth capacity.